Refractory



Patented Jan. 3, 1933 V UNITE-D STATES ATE;

PAUL G. wxnnnrrs, or wn'sr HARTFORD, oonnnorrcunassrenon r nanrronn,

COMPANY, or irnnrroan, connncrron r, A ooarcnarron or DELAWARE I InErnAoronY Io Drawing.

This invention relates to fire bricks and other refractory articles foruse at high temperatures.

The value of fire bricks is determined by 6 their resistance toshrinkage under continu ous hea-tingjand by their resistance tospalling, slagging and deformation under load. I have discovered thatrefractory bricks, tiles and the like, having superior properties in 10these respects, may be produced at low cost fromiwhite' bauxite, GeorgiaKlondike white kaolin and a hard bauxitic fireclay known as Georgia Gclay, by the process described below. The Georgia G clay is the hardclay from Gordon, lVilkinson County, Georgia, referred to on page ofBulletin 252 of the U. S. Dept. -of Commerce, Bureau of Mines.

The chemical compositions of these three starting materials areindicated inthe following table, which gives analyses of typicalsamples:

Georgia lVhite Klondike Georgia 7 bauxite white G1 clay kaolin Loss onignition 24. 13 75 15. 63 A'lzO; 50. 82 39. 19 36. 59 22. 71 45. 24 44.75 2. l. 61 1. 56 0. 53 0. 43 1. 22 0. 18 Trace 0. 42 0. 01 None 0 17 0.10 0.60 0. 10

It will be noted that-all three :of-these materials are low in "fluxes,particularly in iron and alkalies.

' I have also discovered that, in commercial practice, the mostdesirable balance of properties may be obtained in the bricks if thebricks have an alumina-silica ratio of about 56 par-ts of alumina toabouttO parts of silica. This proportion of alumina and silica producesa product which is more rigid and has less constant shrinkage thanbricks having a higher content of, alumina, and such bricks also have agreater load capacity than bricks higher in alumina. It has long beenrecognized in the art that bauxite and 'bauxitic clays theoreticallyshould product refractory bodies of great value. It has been known thatApplication filed July 21, 1928. Serial No. 294,601.

bauxite, for example, containing, as it does, a highly desirableproportion of aluminaand silica and a relatively low flux content, w1lltheoretically-by itself for-m a superior refr'actory body, if calcinedto a point at which its characteristic constant shrinkage may be.

eliminated and the body stabilizedf This, however, cannot be doneceramically at commercially obtainable temperatures. 7

In the past, the refractorinessof bauxite and'bauxitic clays has'beenrecognized by nearly every manufacturer of refractories, and it seemssafe to say that'at sometime, substantially all of these manufacturers,and their ceramists, have attempted to form a superior refractory bodyby the use of tan ite and bauxit-ic clays.- But'while refractory brickshave from time to time appeared on the.

market formed from bauxite, there are at the present time few successfulones on the mar ket. The reasons for th1s commercial failure of bauxitebricks are stated in part by'Searle,

Refractory Materials, Their Manufacture and Uses, 1924, Charles Gri-fiin& Co., Lt-d., page e09, as follows:

Shrin7cage.Thechief drawback of bricks containing a large proportion ofbauxite is their continual shrinkage when in use at high temperatures.Even when bauxite bricks have been burned at the highest temperatureattainable in akiln, they still continue to shrink when in use, and ithas hitherto been found almost impossible to produce bauxite bricks ofperfectly constant volume. If the temperature at which the bricks wereburned during manufacture is below that correspond; ing to Seger cone10, the shrinkage of the bricks in use may be serious; with a higherburning temperature the shrinkage in use will be less, but it will stillbe noticeable, Finer particles ofbauxite are more constant in volume onrepeated heating than are the coarser ones.

The shrinkage of bauxite can. be reduced by the addition of quartz, butthis lowers the refractoriness of the bauxite and so produces brickswhich are little, if any, better than those made of fireclay. Hence, theaddition of silica to bauxite is not to be recommended;

- istic bauxite tendency of constant shrinkage,

even at temperatures lower than the firing temperature. Thus it isevident that before such a mixture could possibly be stabilized, itwouldhave to be raised to a temperature at which bauxite, per se, wouldbe stabilized and this, as pointed out above, is commerciallyimpossible. Y

My invention comprises, as far as-I am aware, the first successfulproduction of a super-refractory in which the refractory character ofbauxite and bauxit-ic clays is used in a composition which, when burnedat commercially obtainable temperatures, namely 2800 to 2900 F. willresult in a stable body in which the constant shrinkage due to thebauxite is not present, and which blocks have superior resistance tospalling, cracking, etc b r Contrary to the prior practices, I so distribute the eutectic-lowering effect of the fluxes in the mixture as tocompletely convert all of the alumina contained in the bauxite orbauxitic clay into mullite at commercially possible temperatures, andsimultaneously form a glassy matrix having a high point of fusion and inthis manner, 'I am enabled to employ materials having unusually low ironand alkalimetal oxide contents. Thus, durlng the process, I destroy theidentity of the starting materials-and produce a homogeneous mass byeffecting chemical reactions and combinations which cannot take placewithout this destruction. The end product which I obtain diflers fromany prior product 7 formed from bauxite or bauxitic clays in that itcontains but two phases, namely, mullite crystals and a glassy matrix,while all previous bricks made from these materials have resulted in atleast three-phase end products. The fusion pointand the porosity aresufiiciently high for all practical purposes in bricks having this ratioof silica to alumina.

A very desirable refractory, known as .No. 10, may be made by mixing thethree starting materials in the proportions of about 55% of whitebauxite, about 35% of Georgia Klondike white kaolin, and about 10% ofGeorgia G clay. These proportions may be varied 1 within one or two percent. above or below satisfactory batch may be made up of Parts byweight Raw white bauxite 128 Raw Georgia Klondike white kaolin 87 RawGeorgia G clay 21 These ingredients are ground to extreme fineness,suitably such as to pass through a standard U. S. No. 325 screen, andare intimately" mixed in the presence of water,'by blunging, repeatedpugging or other suitable methods, to produce intimate association ofthe three ingredients. then formed into pieces suitable for handling,which are calcined at a temperature of about 285 F. or higher, and thecalcined product is then broken down to form grog, this grog b ingsuitably made fine enough to pass through a standard U. S. No. 8 screen.

-About 60 parts of the grog thus prepared is mixed withabout 40 parts ofthe abovedescribed raw mixture, which may itself be mixed either wet ordry and the-assembled material is dry-pressed under moderate pressure,of the order of two tons per square inch, to form the desired bricks orother shapes. The material, when pressed, should contain about 8% ofwater. The pressed bricks or other shapes are then dried and fired atatemperature of 2850 F. or higher.

The white bauxite, while highly refractory, has a high, continuous andever-present shrinkage at high temperatures, does not become impermeableuntil about 325Qf F. and is substantially non-plastic, so that 1t hasonly slight mechanical strength. The Klondike clay is a soft white andnon-plastic kaolin. It offsets the shrinkage of the bauxite 1n brickswhich are fired at about 2850 and performs the further functions ofaddmg to the silica content of the product and produclng rigidity underhigh temperatures. This kaolin alone does notbecome impermeable below2800 F.,;has a softening point ofcone 34, and has only slightmechanicalstrength when raw modulus of rupture only 15 lbs, per sq'.in.) The G bauxitic clay has a considerable degree of plasticity andperforms the functions in this mixture of still further adding to thesilica content and producing rigidity under heat, but is primarily usedto give the initial mixture sufiicient temporary strength for moldingand handling. The Gr clay also contributes to the final mechanicalstrength of the product. It too has a fusion point of cone'34: andis-extremely resistant to spalhng.

The pressure under which the final assembly is dry-pressed is somewhatcritical and for bcstresults should be from 1 ton to 2% tons per squareinch, preferably about 2 tons. Higher pressure, of the order of 5 tonsper square inch, for example, gives a denser product and one having agreater load-carrying capacity, but such a product is less resistant Themixed material is i seegaiez tospallinigonaccountofiitsagreaterpdensity:

Thee-properties theebri-c-ks: produced' fby; thiSvSPQGlfiQPIOGGSSgare'indiated :inathe'fol? lowingitable, Whichalsogivestl1e1correspond+i inggproperties ofian lordinary con-imercialfire+ brick-4offtheehighestpgrade, and. ofraehighly, alumiiious-commercial firebrick;

for one hr. at-2786 F3 pression.- Load test;(50lbsv per Sq-.;in.).5.1%co111- i.

pression l f $287693 Mellon: Institute standard: No. spell: 8% 9.

spelling te 1 h1g9- 1tI=el1on.- I1istitute1 standard q slaggnigitests"Natrattacked Z 1 87. 9%: 85.-'9% 84. 3%,;

It'iseN-identfrom these properties and test results that these briekshave 'extra'ordinary abilityto-withstand the most severe oon distionsmfservaoe, and this-has been shown also actual use in furnaces,- in1 whioh these 99" bricks 1 have withstood temperatures as high as 3206 M3300? F1 repeated' heating and cooling, and "seve-re meelianica-lshocks; for

long *peri ods of: time and with less 4 than 1% shrinkage? H v 5*Mieroseo qie examination of th is product slrows th'at it'is composed'0f' tW0 constituentsor ph-ases' 01113 a orystalline constituent hawirrgthe optical properties of m-nllite (8Alg .-2Si@4 and a glassyconstituent:

The crystalline constituent occurs; invery" S1 minute or sta-ls theaverae si-Ze ofwhiehisfllOO P; X 0.'0Q1"-1nm.j QOecasionally largermrysta lsa're" seen; the --1naxiinum size being about 0.015 mm. X 01002 111111The N crystals' are- Very unifornig in size 41nduniforiirly-'distrihutedf through the massi" They show p a-ralIl= e2'tinetion positii e eloirgatioii and an average index o-f 're-fraeti0i1'of about 15651 T-his index ndieates-th at the crystals.

58 I are nearly pure miillite ii composition and containverylittle F 0;or TiOf-g insolidso lutionz- Thereforethese-oxides, and the bases shownb y analysis, appearito beall inthe', glass. Another-desirable productof the san1e-generaltype,lnown as-No. 9".may be made by mixing the samethree starting materials" in alioutthe proportions of white. bauxite,10% Georgia Klondike. White kaolin and '10 oorGeorg iai G clay. EoreXanipl athe hatch maycontaiii. v I v Parts by V in Raw-whitebauxiteinue -;i ii; il RawGeorgiarKlondikeew-hitev aol-in 21 5 1Raw; (leorgiaqGr aclay 'sn d; -42 211 as well;as'thefl\ o. 10?materiali'.

. This imi-xtureuis for-med intorgrogggas'semhled; withfiddiitiiOHfllil'fiW binder; dry-pressed; and fired iii the "manner?described aboveoini conneotionrW-itlr the; firstaexainple r 'llre-zree;-sulting p groduot' is SlightlyKIIIOIGPOI'OllSithflIl i 7.0 the productfirst: described. Iti? withstands the: l0a'd;1spalling; and.slaggingftests. nearly f The: chemical; compositions; of; the: two;

products: .s'electedlfor: illustrationare; shown: 751.

1 No.9"? No. 10

Lesson ignitionr 22'! 28' 8'6" SiO"; 34s 89 39. 90 A1201 61. 39 56.38F8203. 1,,11 89", TiOy.-- 2.72 2.65" 020... I .28: 23-: Mg0- .27-- .25NazO -i None: .106:

It is partieularly to be noted' thatrthese produets containonlys'malla-m-ounts' 'o fironi Thus the formulation of theirawhatch-ma n bezsooontrolled-as -.to.-con tain a minimum of approximately: 9.6% totalalumina and silica ofnvhich preferably F5.6&%. or .more is-alumina,

a minimum-total oftapproximatelyyl% ,iron; and alkali metal oxides-andthebal anoe, ,(ap

proximately 3%) stal -impurities as titanium and. alkaline earth metaloxides: Gonse 12o.

qtiently oontrol of end :product compositions is made possible. withinsimilari limits, even though .theyare suhjeetj-to some; slight maria?tions as the result of the handlin glandtfiringg ofthe btatoli'material, asrshownibytherialcove typical lend vproduct compositions;

T-h'e use of the; Georgia- Klondike' kaolin is especially important"regulating rthe coinpos'ition aas aforesaidiloeeause: the {amount of:-bauxite used is: ifixedxhetween' relatively-Hare 139 Norio- Nd-9 it 5X2840.: I I

2.53 2590;. m5 -.68 v .74; .16 .23 .02 I .02; .33: .19

00. 1; 101x1 8 1 6.4 96.1/ Total Feo3+Na4o 1; 01 93% 119 Balance 2. 11%3.15

row limits by the desired alumina content, and the amount of plasticclay introduced into the batch is restricted by its relative highcontent of certain impurities, although its use is highly advantageousin other respects.

The extent of chemical Control afforded by the batch composition of theinvention is par ticularly significant in View of the fact that it isunusually refractory, and when treated substantially as above described,will mature at a relatively low temperature such as 2850 F.; that is, atsuch'temperature, after-shrinkage, discussed above, completely iseliminated. That is advantageous as a practical matter becauseespecially designed and constructed kilns need not be employed in firingthe end products; such a maturing temperature may readily be obtained inpractice and readily controlled.

' In the appended claims, the starting materials are, for convenience,referred to specifically as White bauxite, Georgia Klondike whitekaolinand Georgia G clay. It will be understood that these designationsinclude 4 all bauxites and clays having approximately the analyticalcompositions stated above for these particular materials, and that myinvention includes the use of such equivalent bauxites and clays, ormixtures of otherclays having the approximate analytical compositionsand properties of'the specific mixtures described above. o.

I claim as my invention:

1. A batch mixture for a ceramic bauxitic refractory comprising unmeltedbauxitic mineral having the characteristics of Georgia o white bauxite,non-plastic kaolin having the characteristics of Georgia Klondikekaolin,

and-plastic clay having the characteristics of Georgia G clay, all in astate of impalpable fineness, said mixture having a maturing temperatureas low as approximately 2850 F. 2. A batch mixture according to claim 1wherein the ingredients are present in such, proportlons, and WlllCllCOIItaIHS such a quantity of the bauxitic mineral, that said batchmixture contains approximately 56% or more alumina.

3. A batch mixture fora ceramic bauxitic refractory comprisingapproximately 55 to 80% bauxitic mineral having the characteristics ofGeorgia white bauxite, approximately 35 to 10% kaolin having thecharacteristics of Georgia Klondike kaolin, and approximately 10%plastic clay having the characteristics of Georgia G clay, all in astate of impalpable fineness, said batch mixture ;'having a maturingtemperature as low as approximately 2850 F. I

4. The processof preparing a batch mixture for ceramicrefractories'which comprises grinding to impalpable fineness unmeltedhighly aluminous material consisting principally of aluminum hydratemineral of the bauxite group, raw plastic bond clay, and

and said'materials will combine with sub-- stantial homogeneity whensubsequently fired, preparing a mixture of the said materials containingthe unmelted highly aluminous material, a lesser quantity of-the rawclay filler to' give the material suitable characteristics forsubsequent handling, and a still lesser quantity of plastic bond clay,and

sufiicient aluminous material, to produce" a mlxture containing 1nexcess of 50% alumina,

intimately mixing said assembled materials in the presence of water,pugging thematerial',and separating the pugged material into piecessuitable for handling and'drying:

5. The process of preparing a batch mixture for a ceramic bauxiticrefractory which comprises grinding to impalpablefineness bauxiticmineral, and clay having such characteristics that when treated with themineral as hereinafter stated, the batch mixture will mature at atemperature as low as approximately 2850 F., the mineral and clay beingground to such fineness that substantially all of each of them will passthrough a screenof the order of a No. 325soreen and will combine withsubstantial homogeneity whensubsequently fired, assembling said mineraland clay in such proportions as to provide amixture contalning 1n thedry state a minimum total of 96% alumina and silica of whichapproximately 56% or more is alumina, a maximum total or approximately1% iron and alkali metal oxides, and the balance such impurities astitanium and alkaline earth metal 6. A batch mixture fo r 'a ceramicrefractory comprising, unmelted bauxitic mineral having thecharacteristics :of Georgia White bauxite, non-plastic kaolln havingstate of impalpable fineness, said mixture containing a minimum total Iof approximately 96% alumina and silica of which approxi--.

mately 56% or more is alumina, a maximum total of approximately1% ironand alkali,

metal oxides, and the balance such impurities as titanium and alkalineearth metal oxides, which batch mixture has a maturing temperature'aslow as' approximately 2850 F.

7. A batch mixture for a ceramic bauxitic refractory comprisingapproximately 55 to 80% bauxitic mineral having the characteristics ofGeorgia white bauxite, approximately 35 to 10% kaolin having thecharacteristics of Georgia Klondike kaolin, and approxi-- thecharacteristics ,of Georgia- Klondike kaolin, and plastic clay havingthecharacteristics of Georgia G clay, all'in a mately clay having thecharacteristics of Georgia GP clay, all in a state of impalpablefineness, said mixture containing a minimum total of approximately 96%alumina and sili- 5 ca of which approximately 56% or more is alumina, amaximum total of approximately 1% iron and alkali metal oxides, and thebalance such impurities as titanium and alkaline earth metal oxides,which hatch mixture 1 has a maturing temperature as low as approximately 2850 F, v

Signed at Hartford, Connecticut, this 20th day of July, 1928.

PAUL G. WILLETTS.

GERTH HCATE GF CORRECTIUN Patent No. 1,893,313. January 3, 1933.

PAUL G. WILLETTS.

it is hereby certified that error appears in the printed specificationof the above numbered oateet requiring correction as follows: Page 3,after line 98, insert the ioiiowing paragraphs:

"With further regard to the compositions of the end products, it ischaracteristic oi the invention that exceptional control of suchcompositions Within certain iimits is afforded by the use oi ingredientshaving the characteristics of those which have been mentioned,especially when employed in the propertions given above.

That is siiowri icy the ioilowing' data on the calculated chemicalcompositions of tixe batch mixtures for the "No. 10" and "No. 9"reiractories, de rived from tire above percentage compositions of saidmixtures, and the foregoing tyoicai ariaiyses of the separateingredients, and reduced to dry basis:

Anti that "it? said Letters Patent should be read with this correctiontherein that tize some may conform to the record of the case in thePatent Office.

Signeti and seaietl this 9th day of May, A. D. 1933.,

J. Moore. (Seal) Acting Commissioner of Patents,

